Synchronizing generator



R. L. 'CAMPBELL SYNCHRONIZING GENERATOR Filed Feb. 15, 1939 vooo'ool kommen..

Ric* qd l.

mbo.

Patented July3, 1940 PATENT; loll-lficE SYNCHRONIZING GENERATOR I "imams An campbell, Hasbrouck heights, N. J., assignor to Allen B. Du Mont Laboratories, Inc., lassaic, N. J., a corporation of Delaware Application February 15, 1939, Serial No. 256,468

(ci. 25o-a6) 6 .Clalma My invention relates to improvements in synchronizing generators of the type more particularly adapted for controlling the horizontal and vertical deiiecting circuits in television come municating systems ng cathode-ray tubes.

One. of the obiects of my invention is to provide an improved generator of the character referred to in which the relation of the two frequencies is maintained moreA accurately and in a 10 simpler way than has been the case heretofore.

Other objects and advantages will hereinafter appear.

The drawing is a simplified, diagrammatic showing of a'synchronizing generator constructed '15 and operating in accordance with my invention.

In the drawing, the reference numeral Iii designates a frequency-control tube for a master oscillator II which is adjusted to generate an electrical wave at 26,460 cycles. A frequencyreducing or frequency-divider circuit I2 which is supplied from the masteroscillatorv as represented, and which may be of any suitable, conventional construction, operates to derive in the output line I3 electrical synchronizing pulses at 60 cycles for the vertical sweep circuits, and electrical synchronizing pulses at 13,230 cycles in the output line I l, for the horizontal sweep circuits. A Thyratron I5, controlled with a 60cycle alternating-current line I6, generates a. 60cycle saw-tooth wave in the output line Il. 'Ihe tube I5 is gas-lilled. i v

The 60cycle pulse output from the line I3 is applied-to the grid of an amplifier tube I8, and the 60cycle saw-tooth wave in the'output line I1 from the Thyratron I5 is applied to the grid of an amplier tube I9. The tubes I8 and I9, which supply a detector tube 2li, constitute a mixer circuit in which the 60cycle pulse and the 60cycle saw-tooth wave are added. l There is thus developed, in the output line 2I fromI the detector, a direct-current potential' which varies in accordance with the relative phase conditions of the two waves. Thisvarying direct-current potential is. applied, as shown, to the grid of the frequency-control tube III. vIn operation, a variation in the detector voltage operates to change the grid voltage ofthe control tube IB and shift thev master oscillator frequency in one direction or the other, depending upon which waythe detector voltage varied.

If the frequency of the line I6 decreases, the voltage applied to the control tube I0 becomes less negative, which accordingly reduces the frequency of the master oscillator, and consequently .55 the frequency of the synchronizing pulses in the 'a suitable load resistor 22,'and in this way a u negative voltage is maintained with respect to ground. The negative voltage varies in accordance withthe position of the wave :c superimposed upon the wave y. 'I'hrough a suitable filter 23, which removes m components of the waves :c and y in the output from the diode 20, such output ls applied to the low end of the grid resistor 24 associated with the frequency-control tube I0. Across the resistor 24 is fed a quadrature component of the oscillator voltage, obtained by inserting a resistor 25 in series with the tank condenser, as shown. 'I'he quadrature voltage from the tank circuit is ampliiied in the tube I0 and fed back to the plate of the oscillator I I. In operation, the control-tube grid voltage is 90 degrees leading the oscillator grid voltage,and in the plate it is reversed 180 degrees, so that it then has the same electric effeet as would a variable negative inductance shunting the tank inductance. An occurring variation in" this voltage will, accordingly, vary the oscillator tank tuning, and correspondingly vary the frequency. When the detector output changes, therefore, the frequency of the master oscillator I I is changed in the proper direction to correct the frequency dierence which caused the J0 detector output voltage to shift in the first instance. l

By means of the condenser 26 and the variable resistance 21, the phase of the voltage applied to 3;,

the Thyratron grid 28 may be controlled with respect to the phase of line I6.

Some of the salient features and advantages of my improved synchronizing generator may be summarized as follows: 40

'Ihe tube II and associated parts constitute a v`resonantly-tuned oscillator, which generates a sine wave.

Use of a gaseous triode, such as the tube I5, provides constant output voltage regardless of 4;, voltage fluctuations in line I6. This provides a more stable frequency-control action. In other words, the saw-tooth voltage output from tube I5 is of constant amplitude, whereas the wave insupply line I6 is not.

It is sometimes desirable to use a source of standard frequency on the grid of tube I5 which is not sinusoidal. The saw-tooth4 voltage output of tube-I5 is independent of input wave form, and therefore this device will operate on standardizing voltages of more than one character, without changesin the general arrangement of the circuits of tubes I5, I8, I9 and 20. In some of the synchronizing generators used heretofore, for example, as in the system disclosed in Patent No. 2,132,654 issued October l1, 1938 to Smith, a sine-wave source must be used. My generator works satisfactorily on any kind of a source regardless of wave form, and use of a saw-tooth.

wave is one of the simplest ways of obtaining the desired results.

The control action in my improved generator can be made to take place over a linear slope of the saw-tooth wave, instead of over a small portion of a sine curve in a particular part of the cycle, such as in the synchronizing generators used heretofore, for example, as in the system disclosed in the Smith patent referred to.

As an alternative, in my improved generator extremely sharp range of control can be obtained by operation of control over the fly-back portion of thesaw-tooth wave. This is desirable in some cases where precise phase4 conditions must be maintained with the power supply system.

. The advantages obtained by my improved synchronizing generator are not dependent upon the fact that the tubes I8 and I9 are amplifiers, nor is amplification necessary.

The frequency-control tube I requires relatively less power to control the master frequency because no appreciable current is taken by the grid of tube I0, whereas in the system disclosed in the Smith patent referred to, control voltage is fed to a 2000 ohm resistor. For this reason, in my improved generator, a more sensitive frequency-control action results. The frequencycontrol tube I0 in my generator is a potentiallyoperated' device for the master oscillator Il,

whereas Smiths 2000 ohm resistor associated with the oscillator TI T2 is a current-operated device.

In synchronizing generators such as is disclosed in the Smith patent referred to, a multivibrator type of master oscillator is used, whereas in my improved generator the master oscillator is resonanthr-tuned, and gives a sine wave. In these prior art systems, therefore, the desirable control v arrangement and action embodied in my improved synchronizing generator cannot be used.

The various values of resistance and capacity are given by way of example only, -and may be changed to suit particular requirements.

It will be appreciated that modifications of the disclosed embodiment of my invention are possible without departing from the spirit of my invention or the scope of the claims.

I claim as my invention:

1. In a synchronizing generator, a resonantlytuned master oscillatorfor generating an electrical wave at a relatively high frequency, a frequency-reduction circuit supplied from said oscillator and operating to derive from said electrical wave electrical pulses occurring at a relatively low frequency, an alternating-current supply at said low frequency, an electronic device to which said alternating-current supply is applied and operating to convert the electrical wave of oscillator and operable to-vary the frequency of the latter in either direction, and a connection for applying said direct-current potential to the grid-circuit of said frequency-control tube.

2. In a synchronizing generator, a resonantlytuned master oscillator for generating an electrical Wave at a relatively high frequency, a frequency-reduction circuit supplied from said oscillator and operating to derive from said electrical wave electrical pulses occurring at a relatively low frequency, an alternating-current supply at said low frequency, a saw-tooth wave generator controlled from said supply, amplifier tubes supplied respectively with said pulses and with the saw-tooth wave and having a common output circuit, a rectifier tube the input circuit of which is supplied from said` common output circuit and operating to develop a resultant directcurrent potential which varies in accordance with occurring variations in the relative phase conditions of said pulses and said saw-tooth wave, a frequency-control tube coupled to said master oscillator and operating to vary the frequency oi the latter in either direction, and a connection for applying said direct-current potential to said frequency-control tube to govern operating action of the same.

3. In a synchronizing generator, means for developing electrical pulses at a relatively high frequency and at a relatively low frequency respectively, a source of supplyof an electrical wavesubstantially at said low frequency, an electronic device to which said wave is applied and operating to convert the same to an electrical wave of a substantially different shape than the .shape of said first-named wave and of substantially constant amplitude, means responsive both, to the pulses at said relatively low frequency and to said second-named electrical wave at said low frequency and operating to derive therefrom a resultant control effect, and connecting means for applying said control effect to said inst-named means to vary the frequency of operation thereof in accordance with occurring variations in said control effect.

4. In a synchronizing generator, means for developing electrical pulses at a relatively high frequency and to a relatively low frequency respectively, a source of supply of an electrical Wave substantially at said low frequency, an electronic device to which said Wave is applied and operating to convert the same to a substantially sawtooth electrical wave of substantially constant amplitude, means responsive both to the pulses at said relatively low frequency and to said substantially saw-tooth electrical wave at saidv low frequency and operating to derive therefrom a resultant control effect, and connecting means for applying said control effect to said first-named means to vary the frequency of operation thereof in accordance with occurring variations 'in said control effect.

' 5. In a synchronizing generator, means for developing electrical pulses at a relatively high frequency and a relatively low frequency respectively, a source of supply of an electrical wave substantially at said low frequency, an electronic device to which said wave is applied and operating to convert the same to a substantially sawtooth electrical wave of substantially constant amplitude, an amplifier'tube to the input circuit of which the pulses at said relatively low frequency are applied, an amplifier tube to the input circuit of which the substantially saw-tooth electrical wave is applied, said tubes having a common output circuit, a rectier tube supplied from said common output circuit and operating to derive therefrom a resultant control effect, and connecting means for applying said control effect to said first-named means to vary the frequency of operation thereof in accordance with occurring variations in said control effect.

6. In a synchronizing generator, means for developing electrical pulses at a relatively high frequency and at a relatively low frequency respectively, said means including a resonantly-tuned master oscillator and a frequency-control device coupled to saidgoscillator, a source of supply of an electrical wave substantially at said low fre-V quency, an electronic device to which said wave is applied and operating to convert the same to a substantially sawtooth electrical wave, anainpliier tube to the input circuit of which'the pulses at said relatively low 'frequency are applied, an amplifier tube to the input circuit ofl which the substantially saw-tooth electrical wave is applied, said tubes having a common output circuit,

a rectifier tube supplied from said common output circuit and operating to derive therefrom a resultant control effect, and connecting means for applying said control efect to said frequencycontrol device to vary the frequency of operation of said oscillator in accordance with occurring variations in said control effect.

RICHARD L. CAMPBELL: 

